Content caching device, content caching method, and computer readable medium

ABSTRACT

A first acquisition unit acquires each of the resources defined by the scenario, from locations depending on identifiers of the resources. A judging unit judge, when a resource having same identifier and structure as the resource acquired is existent in the cache storage, erases the resource, the identifier thereof, and the receipt time information from the cache storage, and when not existent, stores the acquired resource in association with the identifier thereof and the receipt time information of the bookmark instruction, in the cache storage. A second acquisition, when the identifiers of the resources specified by a first scenario are existent in the cache storage, acquires the resources from the cache storage according to the receipt time information corresponding to the first scenario and identifiers of the resources, and when not existent, acquires the resources from a location depending on the identifiers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-293854, filed on Dec. 28,2010, the entire contents of which are incorporated herein by reference.

FIELD

The embodiment of the present invention relates to a content cachingdevice, a content caching method, and a computer readable medium.

BACKGROUND

There is known a content synthesizer which synthesizes content bycombination of a plurality of information items (Web resources) on theInternet in order to let a user view the synthesized content as aprogram. This is based on the assumption that the original contentelements such as image, text, sound, moving image, etc. on the Internetare synthesized, based on a design, by a terminal of the user. Here,this design is called a scenario.

There is a case where the user newly views the content which waspreviously viewed by the terminal. When the user wants to view theprogram which was previously viewed by the terminal of the user onceagain, the information must be reserved somewhere. Generally, thefollowing three locations can be used to reserve the information.

(1) a terminal of the user

(2) another terminal of the user

(3) a server

As for (1), a mobile terminal is regarded as a terminal of the user. Inthis case, the terminal is supposed to have a small capacity forreserving information, and thus it is unlikely that the terminal of theuser is used to reserve the information.

As for (2), television or home server in the home, private server of theuser on the network, etc. are regarded as another terminal of the user.However, it is hard to consider that every user has these devices.

As for (3), when a server providing services reserves the information,the server is required to provide the same service to many users.Therefore, the amount of information stored by each user is accumulated,and thus a large amount of information must be reserved. In aconventional technique suggested to solve this problem, the same data isshared among different users. However, in this technique, at least oneinformation item must be reserved in the home or a shared server nearthe user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of a Web resource caching device as a contentcaching device according to the present embodiment.

FIG. 2 shows the operation performed by the device of FIG. 1 wheninstructed to store a bookmark by a terminal.

FIG. 3 shows the operation flow of reserve judgment.

FIG. 4 shows the operation performed by this device when a BM history isrequested.

FIG. 5 shows the operation performed by this device when instructed toreproduce a bookmark.

FIG. 6 shows a data example of the BM history reserved in a BM historystorage.

FIG. 7 shows an example of the data reserved in a cache storage.

DETAILED DESCRIPTION

According to an aspect of embodiments, there is provided a contentcaching device including: a reserve instruction receiver, a bookmarkhistory storage, a first acquisition unit, a cache storage, a judgingunit, a reproduction instruction receiver, a second acquisition unit, amashup unit and an output unit.

The reserve instruction receiver receives a bookmark instruction for ascenario, the scenario defining a method for synthesizing a plurality ofresources each having its identifier.

The bookmark history storage stores the scenario in association withreceipt time information of the bookmark instruction received at thereserve instruction receiver.

The first acquisition unit acquires each of the resources defined by thescenario, from locations depending on identifiers of the resources.

The cache storage stores a plurality of resources, identifiers thereofand receipt time information.

The judging unit judges whether a resource having same identifier andstructure as the resource acquired by the first acquisition unit isexistent in the cache storage, erases, if existent, the resource, theidentifier thereof, and the receipt time information from the cachestorage, and stores, if not existent, the acquired resource inassociation with the identifier thereof and the receipt time informationof the bookmark instruction, in the cache storage.

The reproduction instruction receiver receives a reproductioninstruction for a first scenario, which is one of the scenario in thebookmark history storage.

The second acquisition unit judges whether the identifiers of theresources specified by the first scenario are existent in the cachestorage, acquires, if existent, the resources from the cache storageaccording to the receipt time information corresponding to the firstscenario and identifiers of the resources, and acquires, if notexistent, the resources from a location depending on the identifiers.

The mashup unit synthesizes the resources acquired by the secondacquisition unit based on a reproduction instruction for the firstscenario to generate a program.

The output unit outputs the program.

Below, the summary of the present embodiment will be explained. Thepresent embodiment is based on the assumption that a plurality of Webresources such as image, text, sound, moving image, etc. on the Web areacquired and processed by a terminal of a user based on a specificdesign so that the Web resources are presented to the user as integratedcontent. In this case, the operation of acquiring and processing the Webresources is called “mashup,” and a design for instructing the mashup iscalled “scenario.” Further, the content created by the mashup is called“program.” Similarly to the programs broadcasted through TV, variouscontent can be assumed: to continuously reproduce text, image, sound,image, etc.; to reproduce only text, image, or sound; to read text; andto wait an input by the user while automatically changing images, forexample.

When using such a terminal, the user sometimes wants to view apreviously viewed program once again. Here, a set including a scenarioand Web resources to be stored for another view is defined as a bookmark(BM). The BM is formed by combining a scenario and a series of Webresources such as image, text, sound, moving image, etc. to be used inthe program or to be required in the mashup process. The Web resource isa single information item identified by URI, and the BM is a combinationof a scenario required to reproduce the program and a single or aplurality of Web resource(s).

The present embodiment is based on the premise that Web resources on theInternet are synthesized and presented by a terminal of the user. Insuch a structure, the original Web content is provided on the Internet.Therefore, when the user wants to view a program again, the original Webresources may be still provided on the Internet, or may not be providedany more (disappeared or changed).

In the present embodiment, the information judged to have strongpossibility of disappearing from the Internet or being changed is cachedin a content caching device (Web resource caching device), and thecached information is used for another view.

On the other hand, the information of Web resources judged to havestrong possibility of being continuously provided on the Internet is notreserved in the content caching device and is acquired from the Internetagain at the time of another view. In other words, the original Webresources are not required to be reserved by the user, and should beacquired from the Internet again when the user wants to view the programagain.

As stated above, the amount of information to be reserved in a terminalof the user or a server can be reduced, while reducing the possibilitythat the BM cannot be reproduced due to the nonexistence of required Webresources.

Hereinafter, the present embodiment will be explained in detail.

FIG. 1 shows the structure of a Web resource caching device 101 as acontent caching device according to the present embodiment.

The content caching device of FIG. 1 includes: a BM reserve instructionreceiver 102; a scenario storage 103; a BM history storage 104; a mashupunit 105; an acquisition unit (first acquisition unit, secondacquisition unit) 106; a cache storage 107; a judging unit 108; and arequest receiver (reproduction instruction receiver, output unit) 109.Note that the first acquisition unit acquires Web resources wheninstructed to store a BM (explained later), and the second acquisitionunit acquires Web resources when reproducing a scenario. The firstacquisition unit and the second acquisition unit may be physically thesame device or separate devices.

The BM reserve instruction receiver 102 can establish wireless or wiredcommunication with a terminal A. The request receiver 109 can establishwireless or wired communication with a terminal B. The acquisition unit106 can establish communication with a plurality of servers 201 througha network 301 such as the Internet. The terminal A is operated by a userto give an instruction to bookmark a scenario. The terminal B isoperated by the user to give an instruction to reproduce a scenario. Theterminal B may be the same as or different from the terminal A. Thiscontent caching device may be arranged as a server in the home of theuser, or may be arranged on the Internet.

Hereinafter, the function of each block included in this device and theentire operation will be explained using the flow charts of FIG. 2 toFIG. 5.

FIG. 2 shows the operation performed by this device when instructed tostore a bookmark by the terminal A.

The BM reserve instruction receiver 102 receives an instruction to storea BM, transmitted from the terminal A of the user (Step S11). This BMreserve instruction includes an identifier (scenario identifier) foridentifying a scenario.

The identifier is formed of character strings and values to function asURI, for example. The scenario determines a method for synthesizing aplurality of Web resources (reproduction method) by specifying theidentifier (URI etc.) of each Web resource.

The terminal A may give the BM reserve instruction for a scenario whichis being reproduced, or for a scenario which is selected from a list ofpreviously reproduced scenarios. Further, the terminal A may give the BMreserve instruction for a scenario which is specified by another method.

The BM reserve instruction receiver 102 requests the scenario from thescenario storage 103 based on the scenario identifier stored in the BMreserve instruction, and acquires the scenario from the scenario storage103 (Step S12).

In the present embodiment, the scenario storage 103 is arranged in thisdevice, but it may be arranged in a location connected to this devicethrough wired or wireless communication, or may be on the Internet 301.Further, the BM reserve instruction receiver 102 may previously reservea fixed number of scenarios to reduce the time required to acquirescenarios.

The BM reserve instruction receiver 102 transmits, to the BM historystorage 104, a BM reserve instruction including the identifier (useridentifier) of the user giving the BM reserve instruction, the scenarioidentifier, and the receipt time information of the BM reserveinstruction (Step S13). The receipt time information represents the timewhen the BM reserve instruction is given (BM reserve instruction time),namely, the time when the BM reserve instruction is received. The useridentifier may be simultaneously acquired when the BM reserveinstruction is given, or may be separately acquired in an authenticationprocess if user authentication etc. is performed.

The BM history storage 104 receives the BM reserve instruction, andreserves a BM history including a set of the user identifier, thescenario identifier, and the BM reserve instruction time.

FIG. 6 shows a data example of the BM history reserved in the BM historystorage 104.

The BM history storage 104 can reserve a fixed amount of BM history. Inthe example of FIG. 6, the BM history includes reproduction frequencydata. The reproduction frequency is the number of times at which thescenario is reproduced depending on the reproduction instruction by theterminal B. The time data shown in FIG. 6 includes year, date, and time(hour, minute, and second), but all of these items should not benecessarily included. For example, the “year” item may be omitted.

When a certain period of time has passed since receiving the BM reserveinstruction, the BM history storage 104 may erase the data correspondingto the instruction by the user. Further, when data amount exceeds areserve capacity (storage capacity), partial data may be erased. Thedata to be erased may be determined based on the reproduction frequencyof each scenario, the ration (e.g., percentage) of the reproductionfrequency of each scenario in the scenarios, or the BM reserveinstruction time, for example. Alternatively, the data to be erased canbe randomly determined. Data instructed by the user to be stored, ordata having reproduction frequency equal to or larger than a fixed valuemay be excluded from erasure targets.

The BM reserve instruction receiver 102 transmits, to the mashup unit105, the scenario acquired from the scenario storage 103 and the receipttime information (BM reserve instruction time) (Step S14).

Based on the scenario transmitted from the BM reserve instructionreceiver 102, the mashup unit 105 specifies the Web resources requiredfor the mashup of the scenario, (Step S15). The mashup unit 105transmits, to the acquisition unit 106, the Web resources to berequired, namely, acquisition instruction information for instructing toacquire the Web resources specified by the scenario (Step S16). Theacquisition instruction information includes the identifier (here, URI)of each Web resource instructed to be acquired, the BM reserveinstruction time, etc.

The acquisition unit 106 tries to acquire, from the Web resource servers201 on the Internet 301, the Web resources specified by the mashup unit105 based on the identifier of each Web resource (Step S17).

With respect to the Web resource which cannot be acquired from the Webresource servers 201, a cache acquisition request is transmitted to thecache storage 107 (Step S20). The cache storage 107 transmits, to theacquisition unit 106, a corresponding cached Web resource (e.g., Webresource having the same identifier, or related to the same or thelatest BM reserve instruction time) (Step S21).

With respect to the Web resource which cannot be acquired from theoutside and is not cached in the cache storage 107, an acquisitionfailure notification is transmitted to the mashup unit 105. In thiscase, the mashup unit 105 may present the user that the Web resourcecannot be acquired.

In Steps S20 and S21, when a Web resource cannot be acquired from theWeb resource servers 201, the cache thereof is attempted to be acquiredfrom the cache storage 107. However, this process can be omitted sinceit is not the essential. In this case, an acquisition failurenotification should be transmitted to the mashup unit 105.

The acquisition unit 106 transmits, to the judging unit 108, a setincluding the Web resource acquired from the Web resource server 201 andthe acquisition instruction information (BM reserve instruction time,Web resource identifier, etc.) obtained from the mashup unit 105 (StepS19).

At this time, the acquisition unit 106 may calculate a hash value of theacquired Web resource to transmit the hash value to the judging unit108. By transmitting the hash value of the Web resource, change in theWeb resource having the same identifier can be detected at high speed,as will be explained later.

The judging unit 108 determines whether or not to cache the acquired Webresource, based on the data transmitted from the acquisition unit 106(Step S22).

When the judging unit 108 determines to reserve, the Web resource, itsidentifier and the BM reserve instruction time are transmitted to thecache storage 107 (Step S23), and the cache storage 107 reserves thetransmitted Web resource, Web resource identifier, and BM reserveinstruction time (Step S24). At this time, a hash value may betransmitted to the cache storage 107 so that the cache storage 107reserves the hash value.

FIG. 7 shows an example of the data reserved in the cache storage 107.One line corresponds to one record. In this example, Web resourceidentifier, BM reserve instruction time, Web resource data (bits), andhash value of the Web resource data are reserved. Resources having thesame hash value have the same structure (data). The Web resourcereserved in the cache storage 107 is sometimes called simply “cache.”Web resources having the same identifier but having different BM reserveinstruction time are reserved separately from each other. This makes itpossible to obtain a Web resource at a specific time in the past. Notethat a scenario ID may be added to the cache storage 107 in order toidentify the scenario which uses the Web resource, and to consider thereproduction frequency etc. depending on the scenario.

The cache storage 107 may erase data (record) showing that a certainperiod of time has passed since reserving it. Further, there is a methodto erase cache with a fixed probability. In this case, this probabilitymay dynamically vary depending on settings of the user, content of theprogram, BM reproduction rate, and BM reproduction frequency. Further,Web resources which do not affect BM reproduction may be preferentiallyerased. When a scenario is erased by the BM history storage 104, thecache storage 107 may erase resources which are used in the erasedscenario and are not used in the other scenarios reserved in the BMhistory storage 104.

When the judging unit 108 determines not to reserve, the judging unit108 instructs the cache storage 107 to erase the cache (Step S25), andthe cache storage 107 erases the cache together with the Web resourceidentifier, BM reserve instruction time, hash value, etc. relatedthereto (Step S26). The instruction to erase the cache may be given whendetermining not to reserve, or may be given later in order to reduceprocessing loads.

Hereinafter, the reserve judgment process performed in Step S22 will beexplained in further detail.

FIG. 3 shows the operation flow of reserve judgment.

The judging unit 108 receives, from the acquisition unit 106, a Webresource (or hash value if has been transmitted), the identifier of theWeb resource, and the BM reserve instruction time included in theacquisition instruction information (Step S31).

The judging unit 108 judges whether a resource having the sameidentifier as the Web resource was requested in the past (S32). This isrealized by confirming whether the same identifier as the Web resourceis reserved in the cache storage.

When judging that the Web resource was not previously requested, thejudging unit 108 determines to let the cache storage 107 reserve the Webresource (Step S34). The cache storage 107 reserves the Web resourcetogether with its identifier, BM reserve instruction time, and hashvalue.

When a resource having the same identifier as the Web resource wasrequested in the past, the following check is performed.

Judgment is made on whether the structure of the acquired Web resourceis different from that of the Web resource (cache) having the sameidentifier and reserved in the cache storage 107 (Step S33). That is,whether the data (bits) of both Web resources are consistent is judged.When the hash value of the Web resource is transmitted from theacquisition unit 106, the transmitted hash value is compared with thehash value of the cache instead of performing data comparison, whichrealizes high-speed judgment.

In the judgment in Step S33, when the structure of the acquired Webresource is different from that of the stored Web resource (cache), theacquired Web resource is determined to be reserved in the cache storage107 (Step S34). The cache storage 107 reserves the Web resource togetherwith its identifier, BM reserve instruction time, and hash value.

When the structure of the acquired Web resource is consistent with thatof the stored Web resource (cache), the BM reserve instruction time ofthe cache is checked (Step S35).

If the time when the cache was stored is later than a time point whichis earlier than the target BM reserve instruction time (transmitted fromthe acquisition unit 106) by a certain period of time, that is, when thetime difference between the BM reserve instruction time of the targetand the BM reserve instruction time of the cache is smaller than athreshold value, the cache and the data related thereto are erased, andthe acquired Web resource is determined not to be reserved (Step S36).

Here, a certain period of time means a relatively long period such asone month. When a Web resource is instructed to be acquired a pluralityof times and the Web resource obtained from the Web resource server isnot changed during this period, if the interval is short, it canestimate that the interval until the next acquisition instructionbecomes short and that the Web resource is not changed (namely thesame), which lead to the judgment to erase the cache.

On the other hand, when the BM reserve instruction time of the cache isearlier than the point which is earlier than the target BM reserveinstruction time by a certain period of time, that is, when the timedifference between the BM reserve instruction time of the target and theBM reserve instruction time of the cache is equal to or larger than thethreshold value, it is determined to continuously reserve the cache andnot to reserve the acquired Web resource (Step S34). This is called afirst method. In this case, as an alternative method, the BM reserveinstruction time of the cache may be updated to the BM reserveinstruction time of the target (second method). Further, it is alsopossible to store only the BM reserve instruction time of the target andthe identifier of the Web resource in the cache storage 107 in order toobtain the main body of the Web resource data (bits) by referring to thecache (third method). In the third method, a field for the ID of therecord to be referred to should be added in the table of the cachestorage.

The first method and the second method are effective to reduce thecapacity of the cache storage as much as possible. Under the premisethat once the content (structure) of a certain resource on the Internetis changed, the resource does not have the original content again (orwith extremely low possibility), when reproducing a scenario related tothe cached BM reserve instruction time or the target BM reserveinstruction time, it becomes extremely likely that the content at thetime of the given instruction can be identically reproduced. The thirdmethod slightly increases the capacity of the cache storage 107 comparedto the first and second methods, but this is a technique realizing amore reliable reproduction.

The above explanation made using FIG. 2 concerns the operation when a BMreserve instruction is made. Hereinafter, the operation when reproducinga BM will be explained. When reproducing a BM, the terminal(hereinafter, the terminal B) required to reproduce the BM acquires a BMhistory (BM list) from this device and specifies the BM to be reproducedin the BM list.

FIG. 4 shows the operation performed by this device when a BM history isrequested.

FIG. 5 shows the operation performed by this device when instructed toreproduce a bookmark.

In FIG. 4, first, the terminal required to reproduce a BM (hereinafter,the terminal B) transmits a request for browsing the BM history to therequest receiver 109 (Step S41). Note that the reproduction terminal Bmay be the same as or different from the terminal A giving BM reserveinstructions. In this way, when a user bookmarks the content viewedthrough a mobile terminal out of the house, the user after returninghome can successively or newly enjoy the content by a big-screen TV withfiner information.

The request receiver 109 transmits a request to acquire the BM historyto the BM history storage 104 (Step S42).

The BM history storage 104 transmits the BM history to the requestreceiver 109 (Step S43). The BM history includes a plurality of BMs.

The request receiver 109 transmits the BM history to the terminal B(Step S44). The terminal B presents this BM history to the user to letthe user select a BM to be reproduced, namely, a scenario to bereproduced. The scenario selected to be reproduced corresponds to afirst scenario.

In FIG. 5, when the BM to be reproduced is specified by the user, theterminal B transmits a BM reproduction instruction to the requestreceiver 109 (Step S51).

The request receiver 109 receives the reproduction request, andtransmits the receipt time information (BM reserve instruction time) andscenario of the specified BM to the mashup unit 105 (Step S52).

The mashup unit 105 performs the mashup of the scenario. First, themashup unit 105 specifies the Web resource specified by the scenario andrequired for the mashup (Step S53), and transmits a request foracquiring the specified Web resource to the acquisition unit 106 (StepS54). The acquisition request includes the BM reserve instruction timeand the identifier of the Web resource required to be acquired.

Based on the BM reserve instruction time and Web resource identifier,the acquisition unit 106 transmits a request for acquiring the cache tothe cache storage 107, (Step S55). This cache acquisition requestincludes the BM reserve instruction time and the Web resourceidentifier.

The cache storage 107 inspects whether a cache (Web resource) related tothe same identifier as the Web resource identifier and related to thesame time as the BM reserve instruction time is existent (Step S56). Ifexistent, the cache is transmitted to the acquisition unit 106, and theacquisition unit 106 further transmits the cache to the mashup unit 105(Step S57).

At this time, when the first method is used in Step S34 of FIG. 3, ifthe cache is judged not to be existent in this Step S56, the followingprocess may be performed. That is, whether a cache related to the sameidentifier as the Web resource identifier is existent is inspected, andif existent, a previous cache related to the time closest to the BMreserve instruction time is transmitted to the acquisition unit 106.This corresponds to the first method, in which when two Web resourcesare judged to have the same structure in Step S33 of FIG. 3, theoriginal one existent in the cache storage 107 is kept as it is, and theother one (Web resource acquired from Web resource servers 201) iserased. As stated above, this first method is effective in the situationwhere once the content (structure) of a certain resource on the Internetis changed, the resource hardly have the original content again. Notethat even when the original content is restored, no affect is caused inthe operation. When the first method is employed on the premise that theoriginal content is hardly restored, if a plurality of Web resources(caches) judged to have the same identifier are existent in the cachestorage 107 in Step S33 of FIG. 3, only the Web resource related to thetime closest to the target BM reserve instruction time may be selectedto judge whether it is the same or not.

When the second method is used in Step S34 of FIG. 3, similar conceptcan be applied. When no cache is judged to be existent in Step S56, if acache related to the same identifier as the Web resource identifier isexistent, a most recent cache closest to the BM reserve instruction timemay be transmitted to the acquisition unit 106.

On the other hand, when no corresponding cache is existent, the cachestorage 107 notifies the acquisition unit 106 that effect, and theacquisition unit 106 tries to acquire the Web resource from the Webresource servers 201, based on the identifier of the Web resource (S58).When a BM reserve instruction is given, the Web resource has beenacquired at least once (see Step S17 of FIG. 2). Thus, when no availablecache is existent, the Web resource is judged by the judging unit 108that it is not necessary to reserve the cache thereof (see Steps S22 andS25 of FIG. 2).

When the acquisition unit 106 cannot acquire the Web resource, that is,when the Web resource is not existent on the Internet 301, the mashupunit 105 is notified that effect (S58, S59).

When the Web resource can be acquired, the acquisition unit 106transmits the acquired Web resource to the mashup unit 105 (S58, S60).

The mashup unit 105 completes the mashup of the scenario using the Webresources acquired by the acquisition unit 106, and transmits a programobtained as a result of the mashup to the request receiver 109 (StepS61). When there is a Web resource which cannot be acquired, a suitableresource may be arranged in its portion. The suitable resource may bepreviously stored in this device, or may be acquired from a server onthe network by an arbitrary method. For example, it is possible tosearch and use similar information, or to use alternative content suchas advertisement.

The request receiver 109 transmits the program provided by the mashupunit 105 to the terminal B (Step S62).

The terminal B displays the program received from the request receiver109 (Step S63). In this way, the scenario when the BM reserveinstruction is given can be reproduced by the terminal B.

As stated above, in the present embodiment, in Web resources specifiedby the scenario instructed to be bookmarked, the Web resources judged tobe capable of being acquired from the network at the time of anotherview in future are not reserved by this device, which makes it possibleto further reduce the amount of information to be reserved compared tothe conventional case.

In this method, when a Web resource determined not to be reserved by thejudging unit 108 disappears from the Internet or changes, the Webresource cannot be acquired and it becomes impossible to synthesize aprogram same as the scenario for which the BM reserve instruction isgiven. However, the present embodiment accepts such a risk to someextent to reduce the capacity for reserving cache, and thus makes agreat contribution to reduce the reserve capacity of the caching device.

In the present embodiment, Web resources are reserved in the servers onthe Internet, but those may be reserved in the same terminal, a homenetwork, or a LAN. Further, the identifier of the Web resource isassumed to be URI, but it may be file pass, IP address, etc.

Note that the Web resource cache device can be realized by using ageneral computer device as basic hardware, for example. That is, eachelement included in the Web resource cache device may be realized byletting a computer carry out a software (computer program) describinginstructions of each process. In this case, the Web resource cachedevice can be realized by previously installing the computer program inthe computer device or by properly installing, in the computer device,the computer program stored in a non-transitory computer readable mediumsuch as hard disk, memory device, optical disk, etc. or distributedthrough the network. Further, each storage can be realized by properlyusing a storage medium such as internal/external memory or hard disk ofthe above computer device, CD-R, CD-RW, DVD-RAM, DVD-R, etc.

The present invention is not limited to the exact embodiments describedabove and can be embodied with its components modified in animplementation phase without departing from the scope of the invention.Also, arbitrary combinations of the components disclosed in theabove-described embodiments can form various inventions. For example,some of the all components shown in the embodiments may be omitted.Furthermore, components from different embodiments may be combined asappropriate.

The invention claimed is:
 1. A content caching device comprising: areserve instruction receiver configured to receive a bookmarkinstruction for a first scenario, wherein the first scenario isassociated with a plurality of resources each associated with anidentifier; a bookmark history storage configured to store one or morescenarios including the first scenario and first receipt timeinformation relating to when the bookmark instruction is received; afirst acquisition module configured to acquire the resources associatedwith the first scenario, from locations depending on the identifiersassociated with the resources; a cache storage configured to store aplurality of resources, associated identifiers, and second receipt timeinformation relating to when the plurality of resources are stored inthe cache; an evaluator configured to determine, for one or more of theacquired resources, whether a previously stored resource having the sameidentifier as the acquired resource exists in the cache storage and whenthe previously-stored resource exists, to erase from the cache storagethe previously-stored resource, the identifier associated with thepreviously-stored resource, and the second receipt time informationassociated with the previously-stored resource, and store in the cachestorage the acquired resource and the identifier associated with theacquired resource, along with the first receipt time informationassociated with the acquired resource from the bookmark history storageas the second receipt time information associated with the acquiredresource, and when the previously-stored resource does not exist, tostore in the cache storage the acquired resource and the identifierassociated with the acquired resource, along with the first receipt timeinformation associated with the acquired resource from the bookmarkhistory storage as the second receipt time information associated withthe acquired resource; a reproduction instruction receiver configured toreceive a reproduction instruction for a second scenario, which is oneof the scenarios in the bookmark history storage, wherein the secondscenario is associated with a plurality of resources each associatedwith an identifier; a second acquisition module configured to determine,for one or more of the identifiers associated with the second scenario,whether the second scenario identifier(s) exist in the cache storage andif the second scenario identifier(s) exist in the cache storage, toacquire the resource(s) associated with the second scenarioidentifier(s) from the cache storage, and if the second scenarioidentifier(s) do not exist in the cache storage, to acquire theresource(s) associated with the second scenario identifiers from alocation or locations associated with the second scenario identifier(s);a mashup module configured to synthesize the resources acquired by thesecond acquisition module based on the reproduction instruction for thesecond scenario and thereby generate a program; and an output moduleconfigured to output the program.
 2. The device of claim 1, wherein theevaluator is further configured to determine whether a time differencebetween the second receipt time information corresponding to thepreviously-stored resource determined to exist in the cache storage andthe first receipt time information corresponding to the time ofreceiving the bookmark instruction associated with the previously-storedresource is smaller than, larger than, or equal to a threshold value,and when the time difference is smaller than the threshold value, erasethe previously-stored resource from the cache storage and when the timedifference is equal to or larger than the threshold value, not erase thepreviously-stored resource.
 3. The device of claim 1, wherein thebookmark history storage is further configured to store reproductionfrequency of each scenario for which reproduction instructions have beengiven, and to erase one or more of the scenarios when a storage capacityof the bookmark history storage reaches a fixed value or when aninstruction to erase is received, and wherein the one or more scenariosto be erased have the lowest reproduction frequency.
 4. The device ofclaim 1, wherein the bookmark history storage is further configured tostore reproduction frequency of each scenario for which reproductioninstructions have been given, and to erase one or more of the scenariosdepending on the reproduction frequencies when a storage capacity of thebookmark history storage reaches a fixed value or when an instruction toerase is received.
 5. The device of claim 1, wherein the bookmarkhistory storage is further configured to erase a scenario based on whena period of time has passed from the first receipt time information forthat scenario.
 6. The device of claim 3, wherein the cache storage isfurther configured to erase a resource that is associated with theerased scenario and that is not associated with another scenario in thebookmark history storage.
 7. A content caching method comprising:receiving a bookmark instruction for a first scenario, wherein the firstscenario is associated with a plurality of resources each associatedwith an identifier; storing, in a bookmark history storage, one or morescenarios including the first scenario and first receipt timeinformation relating to when the bookmark instruction is received;acquiring the resources associated with the first scenario, fromlocations depending on the identifiers of the resources; for one or moreof the acquired resources, determining whether another resource havingthe same identifier as the acquired resource already exists in a cachestorage and when the other resource exists, erasing the other resource,an identifier associated with the other resource, and second receipttime information associated with the other resource relating to when theother resource was stored in the cache, and storing in the cache storagethe acquired resource and the identifier associated with the acquiredresource, along with the first receipt time information associated withthe acquired resource from the bookmark history storage as secondreceipt time information associated with the acquired resource, and whenthe other resource does not exist, storing in the cache storage theacquired resource and the identifier associated with the acquiredresource, along with the first receipt time information associated withthe acquired resource from the bookmark history storage as secondreceipt time information associated with the acquired resource;receiving a reproduction instruction for a second scenario, which is oneof the scenarios in the bookmark history storage, wherein the secondscenario is associated with a plurality of resources each associatedwith an identifier; determining, for one or more of the identifiersassociated with the second scenario, whether the second scenarioidentifier(s) exist in the cache storage and if the second scenarioidentifier(s) exist in the cache storage, acquiring the resource(s)associated with the second scenario identifier(s) from the cachestorage, and if the second scenario identifier(s) do not exist in thecache storage, acquiring the resource(s) associated with the secondscenario identifiers from a location or locations associated with thesecond scenario identifiers; synthesizing the acquired resources basedon the reproduction instruction for the second scenario and therebygenerating a program; and outputting the program.
 8. The method of claim7, further comprising determining whether a time difference between thesecond receipt time information corresponding to the other resourcedetermined to exist in the cache storage and the first receipt timeinformation corresponding to the time of receiving the bookmarkinstruction associated with the other resource is smaller than, largerthan, or equal to a threshold value, and when the time difference issmaller than the threshold value, erasing the other resource from thecache storage and when the time difference is equal to or larger thanthe threshold value, not erasing the other resource.
 9. The method ofclaim 7, further comprising storing reproduction frequency of eachscenario for which reproduction instructions have been given, anderasing one or more of the scenarios when a storage capacity of thebookmark history storage reaches a fixed value or when an instruction toerase is received, wherein the one or more scenarios to be erased havethe lowest reproduction frequency.
 10. The method of claim 7, furthercomprising storing reproduction frequency of each scenario for whichreproduction instructions have been given, and erasing one or more ofthe scenarios depending on the reproduction frequencies when a storagecapacity of the bookmark history storage reaches a fixed value or whenan instruction to erase is received.
 11. The method of claim 7, furthercomprising erasing a scenario based on when a period of time has passedfrom the first receipt time information for that scenario.
 12. Themethod of claim 9, further comprising erasing a resource that isassociated with the erased scenario and that is not associated withanother scenario in the bookmark history storage.
 13. A non-transitorycomputer readable medium storing a computer program which, when executedby a computer, causes the computer to perform acts comprising: receivinga bookmark instruction for a first scenario, wherein the first scenariois associated with a plurality of resources each associated with anidentifier; storing, in a bookmark history storage, the first scenarioand first receipt time information relating to when the bookmarkinstruction is received; acquiring the resources associated with thefirst scenario, from locations depending on the identifiers of theresources; for one or more of the acquired resources, determiningwhether another resource having the same identifier as the acquiredresource already exists in a cache storage and when the other resourceexists, erasing the other resource, an identifier associated with theother resource, and second receipt time information associated with theother resource relating to when the other resource was stored in thecache, and storing in the cache storage the acquired resource and theidentifier associated with the acquired resource, along with the firstreceipt time information associated with the acquired resource from thebookmark history storage as second receipt time information associatedwith the acquired resource, and when the other resource does not exist,storing in the cache storage the acquired resource and the identifierassociated with the acquired resource, along with the first receipt timeinformation associated with the acquired resource from the bookmarkhistory storage as second receipt time information associated with theacquired resource; receiving a reproduction instruction for a secondscenario, which is one of the scenarios in the bookmark history storage,wherein the second scenario is associated with a plurality of resourceseach associated with an identifier; determining, for one or more of theidentifiers associated with the second scenario, whether the secondscenario identifier(s) exist in the cache storage and if the secondscenario identifier(s) exist in the cache storage, acquiring theresource(s) associated with the second scenario identifier(s) from thecache storage, and if the second scenario identifier(s) do not exist inthe cache storage, acquiring the resource(s) associated with the secondscenario identifiers from a location or locations associated with thesecond scenario identifiers; synthesizing the acquired resources basedon the reproduction instruction for the second scenario and therebygenerating a program; and outputting the program.
 14. The medium ofclaim 13, wherein the computer program, when executed by a computer,further causes the computer to perform acts comprising: determiningwhether a time difference between the second receipt time informationcorresponding to the other resource determined to exist in the cachestorage and the first receipt time information corresponding to the timeof receiving the bookmark instruction associated with the other resourceis smaller than, larger than, or equal to a threshold value, and whenthe time difference is smaller than the threshold value, erasing theother resource from the cache storage and when the time difference isequal to or larger than the threshold value, not erasing the otherresource.
 15. The medium of claim 13, wherein the computer program, whenexecuted by a computer, further causes the computer to perform actscomprising: storing reproduction frequency of each scenario for whichreproduction instructions have been given, and erasing one or more ofthe scenarios when a storage capacity of the bookmark history storagereaches a fixed value or when an instruction to erase is received,wherein the one or more scenarios to be erased have the lowestreproduction frequency.
 16. The medium of claim 13, wherein the computerprogram, when executed by a computer, further causes the computer toperform acts comprising: storing reproduction frequency of each scenariofor which reproduction instructions have been given, and erasing one ormore of the scenarios depending on the reproduction frequencies when astorage capacity of the bookmark history storage reaches a fixed valueor when an instruction to erase is received.
 17. The medium of claim 13,wherein the computer program, when executed by a computer, furthercauses the computer to perform acts comprising: erasing a scenario basedon when a period of time has passed from the first receipt timeinformation for that scenario.
 18. The medium of claim 15, wherein thecomputer program, when executed by a computer, further causes thecomputer to perform acts comprising: erasing a resource that isassociated with the erased scenario and that is not associated withanother scenario in the bookmark history storage.